Coal Fly/Bottom Ash, Hydroxylapatite, and Hydrotalcite

Abstract

In this chapter, some inorganic materials such as coal ash, hydroxyapatite, and hydrotalcite are taken up as the adsorbents to remove pollutants in contaminated water and soil. Coal ash is a residual material that exists after all combustible material in coal has been burned. The main components of coal ash are silica (SiO2) and alumina (Al2O3) and other metal oxides also exist. Although coal ash has some ability to adsorb pollutants, the ability increases by activation with acids and modification with an organic ligand like dithizone. The activated and modified coal ash were applied to the adsorption of cationic, anionic dyes and also Hg(II). Hydroxyapatite (HAP), one form of Ca-phosphate compound, is a main component in bone as well as collagen. HAP is an important material biologically and it becomes an excellent adsorbent for arsenate. Firstly, our studies of HAP as the geometrical scaffolds for bone reconstruction are introduced and then the removal of arsenate from environmental water by HAP is discussed using a chromatographic system. Lastly, the adsorbing property of layered double hydroxides (LDHs), which are called hydrotalcite minerals, with the unique structure, is discussed as well as the systhesis methods.